Shredder feeder

ABSTRACT

A document shredder is disclosed including a paper receptacle for receiving a load of paper and a shredding assembly. A metering assembly is interposed between the paper receptacle and the shredding assembly and is configured to separate a portion of the load of paper from the load of paper and permit the portion of the load of paper to move into the shredding assembly. The metering assembly may include a stop plate secured thereto and defining a lifting portion on a perimeter portion thereof. The lifting portion is configured to engage a lower edge of the portion of the load of paper upon rotation of the stop plate and lift the paper over the stop plate. The lifting portion may include a flange, which may be a portion of a cone, formed on a perimeter portion of the wheel and occupying a sector of the perimeter of less than 60 degrees.

FIELD OF THE INVENTION

This invention relates generally to a document shredder. The inventionrelates more particularly to a paper feeding portion of the documentshredder.

BACKGROUND OF THE INVENTION

Document shredders are used to shred confidential or private documentsto prevent unwanted viewing of the document by another. Documentshredders are available in various feed capacities. For a small volumeof documents to be shredded, a document shredder which accepts a singledocument to be shredded at a time may be satisfactory. For a largervolume of documents to be shredded, a document shredder that may acceptmore than one document at a time may be preferable. Document shreddersthat may accept more than one document at a time may have paper feedingmechanisms that feed more than one document at a time to the shredder.However, document shredders that may accept more than one document at atime may be prone to jams in the shredder portion of the documentshredder due to improper feeding of the documents to be shredded. Jamsin the shredder portion of the document shredder may be caused byattempting to feed more documents at one time than the document shredderis capable of shredding, or by attempting to shred documents at a fasterrate than the document shredder is capable of shredding. Therefore, aneed exists in the art for a feeding mechanism for a document shredderthat feeds documents to be shredded at a volume and rate that does notexceed the shredding capacity of the document shredder.

SUMMARY OF THE INVENTION

The present invention provides an apparatus for feeding a controlledamount of documents to be shredded into a document shredder at acontrolled rate. The controlled, or desired amount of documents to beshredded is an amount of documents to be fed into a shredder mechanismof a document shredder that will not normally cause jamming of theshredder mechanism of the document shredder. In some embodiments, ashredder includes a paper receptacle for receiving a load of paper and ashredding assembly. A metering assembly is interposed between the paperreceptacle and the shredding assembly. The metering assembly isconfigured to separate a portion of the load of paper from the load ofpaper and permit the portion of the load of paper to move into theshredding assembly. For example, the paper receptacle may be at a higherelevation than the shredding assembly.

In another aspect of the invention, the paper receptacle defines a ridgethat engages a lower edge portion of the load of paper. The meteringassembly may be configured to urge the portion of the load of paper overthe ridge. The paper receptacle may include a base positioned to supportlower edges of sheets of the load of paper. A support may extendupwardly from a rear portion of the base and the lip may be secured to aforward portion of the base. The paper receptacle may further include abiasing member positioned to urge the load of paper toward the meteringassembly.

In another aspect of the invention, the metering assembly includes ametering shaft having an axis of rotation oriented perpendicular tolower edges of sheets in the load of paper. A stop plate is secured tothe metering shaft and defines a lifting portion on a perimeter portionthereof. The lifting portion is configured to engage a lower edge of theportion of the load of paper. In some embodiments, the stop plate isembodied as a wheel and the lifting portion includes flange secured to aperimeter portion of the wheel. The flange may be embodied as a portionof a cone concentric with an axis of rotation of the wheel. In someembodiments, the lifting portion lies entirely in a sector of the stopplate smaller than 60 degrees with respect to an axis of rotation of themetering shaft.

In another aspect of the invention, a shaft support engages the meteringshaft having the stop plate positioned between the shaft support and thepaper receptacle. The shaft support may further include a ramp securedthereto and defining a ramp surface sloping downwardly from the meteringshaft.

In some embodiments, the shredding assembly includes two cutting bladeassemblies and a motor coupled to the cutting shafts. The motor, or adifferent motor, is also coupled to the metering shaft. The cuttingblade assemblies may shred paper of length L with a linear feed rate Fand be able, or rated, to simultaneously shred a maximum number ofsheets M. The metering assembly may be configured to separate portionsof paper of at most N sheets from the load of paper with a period T. Thevalues of T and N may be configured such that N*ceiling(L/(F*T)) is lessthan M.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred and alternative examples of the present invention aredescribed in detail below with reference to the following drawings:

FIG. 1 illustrates a top plan view of a document shredder in accordancewith an embodiment of the present invention;

FIG. 2 illustrates an isometric view of a drive mechanism for thedocument shredder including a metering assembly in accordance with anembodiment of the present invention;

FIGS. 3A through 3C illustrate a metering assembly in accordance with anembodiment of the present invention;

FIG. 4 is an isometric view of a drive mechanism for a metering assemblyin accordance with an embodiment of the present invention;

FIG. 5 is a partial isometric view of a metering assembly having a shaftsupport in accordance with an embodiment of the present invention; and

FIGS. 6A and 6B illustrate metered release of paper using a meteringassembly in accordance with an embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 illustrates an embodiment of a document shredder 10. The documentshredder 10 includes a feeder portion 12 and a shredding portion 14. Thefeeder portion 12 includes a paper tray 16 and a biasing plate 18. Thefeeder portion 12 and shredding portion 14 may be secured to and/orhoused within a housing 20.

Referring to FIG. 2, the shredding assembly 14 may include a motor 22for driving the shredding assembly 14. The motor 22 may output power toa gear assembly 24 and a gear assembly 26. As is apparent in FIG. 2, thegear assemblies 24, 26 are located on opposite sides of the cuttingblade assemblies 28. The cutting blade assemblies 28 may each includeshafts having a number of blades secured thereto and interleaved withthe blades of the opposing cutting blade assembly 28. The cutting bladesmay be configured according to any embodiment known in the art. In someembodiments, gear assembly 26 is driven by the motor 22 by means of thecutting blade assemblies 28. The manner in which the motor 22 drives thecutting blade assemblies 28 and the configuration of the gear assemblies24, 26 may be according to any embodiment known in the art.

In some embodiments, the motor 22 may drive a gear 30 that actuates ametering assembly 32 for dispensing paper within the paper tray 16.Alternatively, the metering assembly 32 may be actuated by a differentmotor. In the illustrated embodiment, the gear 30 is driven by gearassembly 26. However, in other embodiments, the gear 30 may engage thegear assembly 24 or be coupled to the motor 22 by some other gearassembly or other actuation means.

As will be described in greater detail below, the metering assembly 32dispenses paper 38 from the tray 16 in a controlled manner such that auser is relieved of the task of feeding paper into the shredding portion14 and jamming of the shredding portion 14 is reduced or eliminated. Inthe illustrated embodiment, the paper tray 16 secures to a base 34. Thepaper tray 16 may maintain the paper 38 in a substantially verticalorientation. For example, the tray 16 may be oriented, or selectivelyplaced into an orientation, at an angle of less than 45 degrees,preferably less than 30 degrees, more preferably less than 15 degrees,with respect to vertical when the shredder 10 is resting on a flatsurface. The base 34 may be substantially horizontal when the shredder10 is resting on a flat surface, e.g. within +/−15 degrees ofhorizontal.

The paper 38 may be prevented from sliding off the base 34 in responseto gravity and/or the action of the biasing plate (see FIG. 1) by meansof the metering assembly 32. For example, the metering assembly 32itself may be positioned at one side of the base 34 having the papertray 16 extending from an opposing side such that a lower portion of thepaper 38 is positioned between the metering assembly 32 and the papertray 16. In some embodiments, one or more ridges 36 are secured to thebase 34, such a portion of the base 34 extends between the one or moreridges 36 and the paper tray 16. In this manner, the paper 38 isprevented from falling into the shredding portion 14 due to gravity andthe action of the biasing plate 18. In some embodiments, the meteringassembly 32 may be operable to lift sheets of the paper 38 over the oneor more ridges 36.

Referring to FIGS. 3A and 3B, the metering assembly 32 may include astop plate 40 coupled to a shaft 42. The stop plate 40 may besubstantially planar in a plane perpendicular to the axis of rotation 44of the shaft 42. In the illustrated embodiment, the stop plate 40 has around perimeter. However, other perimeter shapes may also be used. Thestop plate 40 may define a lifting portion 46 operable to lift portionsof a load of paper and allow the portions to fall into the shredder inresponse to rotation of the shaft 44. The lifting portion 46 may lie ina sector of the stop plate 40, with respect to the axis of rotation 44,that is less than 60 degrees, e.g. between 45 and 60 degrees. In thismanner, for a major portion of the period of rotation of the stop plate40, no paper is being lifted, thereby allowing a previous batch of paperto completely or partially pass through the shredding portion 14. Insome embodiments, multiple lifting portions 46 are distributed uniformlyaround the perimeter of the stop plate 40.

In the illustrated embodiment, the lifting portion 46 is embodied as aflange 48 extending from a perimeter of the stop plate 40. The flange 48may be sector shaped in a plane perpendicular to the axis of rotation 44(the plane of the page for FIG. 3B), the sector being centered on theaxis or rotation 44. As is apparent in FIG. 3B, there is an abruptradial step between the flange 48 and the perimeter of the wheel 44. Inother embodiments, a smoother transition between the larger radius ofthe flange 48 and the radius of the wheel 44 may be used. The angularwidth 50 occupied by the flange 48 is less than 180 degrees, preferablyless than 90 degrees, and, more preferably, less than 60 degrees. Forexample, the angular width 50 may be between 45 and 60 degrees. In theillustrated embodiment, the angular width 50 is approximately 55degrees.

Referring specifically to FIG. 3C, as noted above, the flange 48 may beembodied a portion of a conical surface, such as a portion of a conesecured to the perimeter of the stop plate 40, the cone defined by anouter surface at an angle 52 relative to the axis of rotation 44 andsymmetrical about the axis of rotation 44. In some embodiments, theinner surface of the flange 48 may be oriented at the same anglerelative to the axis of rotation 44 as the outer surface. In otherembodiments, the inner surface defines a greater angle such that theflange 48 tapers with distance from the axis of rotation 44.

In some embodiments, the angle 52 may be substantially equal to an angledefined by paper stacked in a shredder with respect to the axis ofrotation 44. For example, the angle 52 may be such that when themetering assembly is positioned within the shredder 10, the angle 52 isequal to the angle defined by the intersection between paper within theshredder 10 and a vertical plane intersecting the axis of rotation 44.In this manner, the flange 48 may more easily slide between sheets ofpaper when dispensing paper.

The outer perimeter of the stop plate 40 may have a radius 54 a and theouter perimeter (relative to the axis of rotation 44) of the flange 48may have a radius 54 b. The difference between radius 54 a and radius 54b may be selected to lift a desired number of sheets per revolution ofthe stop plate 40.

Referring to FIG. 5, as noted above, the shaft 42 may be rotated by themotor 22. For example, the gear 30 engaging the gear assembly 26 mayrotate a lateral shaft 58. The lateral shaft 58 may drive the shaft 42by engagement of a bevel gear 60 a secured to the shaft 58 with a bevelgear 60 b secured to the shaft 42. As is apparent in FIG. 5, the rate ofrotation of the shaft 42 and stop plate 40 relative to the rotation ofthe cutting blade assemblies 28 is determined by some or all of the gearassembly 24, gear assembly 26, gear 30, and bevel gears 60 a, 60 b. Adesired relative rate of rotation of the shaft 42 and cutting bladeassemblies 28 may also be achieved by other means, including electroniccontrol of separate motors or some other means. In some embodiments, acontroller may be operably coupled to the motor 22 and to a sensor 61positioned adjacent the shaft 42 and operable to sense a rotationalspeed of the shaft 42, such as by means of optically detecting one ormore optically detectable markings on the shaft 42, detecting variationin a magnetic field from a magnet attached to the shaft 42, mechanicalactuation of a switch by the shaft 42 for each rotation, or any meansknown in the art for detecting rotational speed.

Referring to FIG. 5, in some embodiments a portion of the shaft 42projects forwardly from the stop plate 40, e.g. away from the base 34.This portion may be engaged by a shaft support 62 defining an aperture64 for receiving the portion of the shaft 42. The shaft support may besecured to the base 34 or to some other structure that is secured to thebase 34, such as the housing 20 or paper tray 16 (See FIG. 1). In someembodiments, the shaft support 62 may be configured to facilitatemovement of paper 38 past the shaft support 62. For example, the shaftsupport 62 may define an angled face 66 that slopes outwardly from thestop plate 40 with distance downward from the stop plate 40. The face 66may define a plane that intersects the stop plate 40, such that papersliding off the stop plate 40 will not catch on any horizontal or othersurface of the shaft support 62. The face 66 may be defined by areas ofthe shaft support 62 surrounding the aperture 64.

FIGS. 6A and 6B illustrate the manner of operation of the meteringassembly 32. Referring specifically to FIG. 7A, as the stop plate 40rotates, the flange 48 secured to the stop plate 40 engage the loweredge of a portion 38 a of a load of paper thereby separating the portion38 a from the rest of the paper 38 b. As the leading edge of the flange48 rises to the apex of its rotation, shown in FIG. 7A, the paper 38 ais lifted above any ridges 36. Referring specifically to FIG. 7B, as thestop plate 40 continues to rotate the portion 38 a of the paper isallowed to fall past the stop plate 40 and any ridges 36 into thecutting blade assemblies 28. In particular, the portion 38 a of papermay be allowed to fall at some point after the leading edge of theflange 48 begins to descend past the apex of its rotation. As notedabove, the biasing plate 18 urges the remaining paper 38 b against oneor both of the ridges 36 and the stop plate 40 ready to be lifted by theflange 48 as the stop plate 40 continues to rotate.

As noted above, the stop plate 40 and cutting blade assemblies 28 may beconstrained to rotate at a fixed relative rate of rotation. The rate ofrotation of the cutting blade assemblies 28 may be effective to achievea linear feed rate F (e.g. length per unit time) of paper through thecutting blade assemblies. The linear feed rate F may be the linear feedof the cutting blade assemblies when shredding a maximum number ofsheets M. In some embodiments, M is the maximum permissible number ofsheets that can be shredded simultaneously between the cutting bladeassemblies 28 at one time without causing jamming of the cutting bladeassemblies 28, failure of the motor 22, or other malfunction of theshredding assembly 14. The value M may be the value specified by themanufacturer of the shredding assembly as the maximum capacity, whichmay be some tolerance below the actual maximum simultaneous sheet limitfor the shredding mechanism 14.

The stop plate 40 may rotate with a period T for the feed rate F suchthat a new portion 38 a of paper drops into the cutting blade assembliesevery period T. The period T may be such that for pages having a maximumlength L multiple portions 38 a of paper may be simultaneously presentbetween the cutting blade assemblies. The number of portions 38 a thatwill be simultaneously between the cutting blade assemblies may be equalto up to Ceiling(L/(F*T)). As noted above, the configuration of theflange 48 (See FIGS. 4A-4C) may determine the largest possible number(N) of sheets that may be lifted by the stop plate 40 per revolution.Accordingly, the largest possible number N of sheets and period T may beselected relative to the feed rate F such that N*Ceiling(L/(F*T)) isless than M.

While the preferred embodiments of the invention have been illustratedand described, as noted above, many changes can be made withoutdeparting from the spirit and scope of the invention. For example,although the feeder portion 12 is shown operating in combination with ashredding assembly 12, other sheets of material may be processedaccording by other material processing apparatus. Accordingly, the scopeof the invention is not limited by the disclosure of the preferredembodiment. Instead, the invention should be determined entirely byreference to the claims that follow.

1. A shredder comprising: a paper receptacle for receiving a load ofpaper; a shredding assembly; and a metering assembly interposed betweenthe paper receptacle and the shredding assembly, the metering assemblyconfigured to separate a portion of the load of paper from the load ofpaper and permit the portion of the load of paper to move into theshredding assembly.
 2. The shredder of claim 1, wherein the paperreceptacle is at a higher elevation than the shredding assembly.
 3. Theshredder of claim 2, wherein the paper receptacle defines a ridge andthe metering assembly is configured to urge the portion of the load ofpaper over the ridge.
 4. The shredder of claim 3, wherein the paperreceptacle further comprises: a base positioned to support lower edgesof sheets of the load of paper; and a support extending upwardly from arear portion of the base, the ridge being secured to a forward portionof the base.
 5. The shredder of claim 1, further comprising a biasingmember positioned to urge the load of paper toward the meteringassembly.
 6. The shredder of claim 1, wherein the metering assemblycomprises: a metering shaft having an axis of rotation orientedperpendicular to lower edges of sheets in the load of paper; a means forrotating the metering shaft; and a stop plate secured to the meteringshaft and defining a lifting portion on a perimeter portion thereof, thelifting portion configured to engage a lower edge of the portion of theload of paper.
 7. The shredder of claim 6, wherein stop plate isembodied as a wheel and wherein the lifting portion comprises a flangeformed in a perimeter portion of the wheel.
 8. The shredder of claim 7,wherein the flange comprises a section of a cone secured to theperimeter portion of the wheel and extending toward the paperreceptacle.
 9. The shredder of claim 6, further comprising a shaftsupport engaging the metering shaft having the stop plate positionedbetween the shaft support and the paper receptacle, the shaft supporthaving a ramp secured thereto and defining a ramp surface slopingdownwardly from the metering shaft.
 10. The shredder of claim 6, whereinthe lifting portion occupies a sector smaller than 60 degrees of thestop plate with respect to an axis of rotation of the metering shaft.11. The shredder of claim 6, wherein the shredding assembly comprises:two cutting blade assemblies; and a first motor coupled to the cuttingshafts; wherein the means for rotating the shaft is a second motor. 12.The shredder of claim 6, wherein the shredding assembly comprises: twocutting blade assemblies; a motor coupled to the cutting shafts; and agear assembly coupling the motor to the two cutting blade assemblies andto the shaft.
 13. The shredder of claim 12, wherein: the gear assemblyis configured to rotate the two cutting blade assemblies effective toachieve a linear feed rate (F) through the two cutting blade assemblies;the lifting portion is configured such that the portion of the load ofpaper includes at most N sheets of paper; the shredder has a sheetshredding maximum of M sheets; the load of paper has a sheet length ofL; and the gear assembly is further configured to rotate the meteringshaft with a period (T) such that N*ceiling(L/(F*T)) is less than M. 14.An assembly for dispensing sheets of material, the assembly comprising:a base positioned to support lower edges the sheets of material; asupport extending upwardly from a rear portion of the base, a ridgebeing secured to a forward portion of the base and configured to retainthe sheets of material; a biasing member positioned to urge the sheetsof material toward the ridge; a metering shaft having an axis ofrotation oriented perpendicular to the lower edges of sheets ofmaterial; a stop plate mounted to the metering shaft and including alifting portion configured to lift a portion of the sheets of materialat a first rotational position of the shaft and rotation of the shaft;and means for rotating the shaft.
 15. The assembly of claim 14, whereinthe lifting portion comprises a flange extending from a circularperimeter of the stop plate.
 16. The assembly of claim 15, wherein theflange is a portion of a cone concentric with the circular perimeter ofthe stop plate.
 17. The assembly of claim 14, wherein, the liftingportion lies within a sector of the stop plate that is less than 60degrees about an axis of rotation of the metering shaft.
 18. A methodfor dispensing sheets of material, the method comprising: placing a loadof sheets of material in a receptacle having the sheets of materialoriented at an angle less than 45 degrees from vertical; actuating ametering assembly including a stop plate and a lifting portion securedto the stop plate to periodically urge portions of the load past thestop plate according to a metering period such that the portions of theload are allowed to fall past the stop plate, the metering assemblybeing positioned at a lower edge of the load of sheets of paper; andreceiving the portions of the load in a material processing assemblypositioned below the stop plate.
 19. The method of claim 18, wherein: amaterial processing assembly has a linear processing rate F and amaximum simultaneous sheet limit M; and the metering period (T), amaximum number of sheets of material (N) in each portion, and a maximumlength (L) of the sheets of material, are such that N*ceiling(L/(F*T))is less than M.
 20. The method of claim 1, wherein actuating a meteringassembly further comprises: rotating a shaft having the stop platesecured thereto and having an axis of rotation thereof orientedperpendicular to the lower edges of sheets of material.